Improvement in coating zinc with lead



Uwrrno STA-res PATENT OFFICE.

E. MOREVOOD AND G. ROGERS, OF LONDON, ENGLAND.

IMPROVEMENT IN COATING ZINC WITH LEAD.

Specification forming part of Letters Patent No. 9,8l8, dated June 28, 1853.

To all whom it may concern:

Be it known that we, EDMUND MoREwooD and GEORGE ROGERS, both of the cityot'London, England, have invented a new and useful Manufacture, being Sheet-Zinc Uoated with Lead, of which the following is a specification.

As lead is less afi'ected by exposure to the atmospheric gases or acids than zinc, and zinc is lighter, stronger, and harder than lead, the zinc coated with lead offers the advantages of more stiffness and strength with less weight and cost than sheet-lead, and is more durable and easily worked than sheet-zinc. The thickness of the compound sheet of lead and zinc, which we use for roofing, for example, varies from one pound to two pounds per superficial foot, and we prefer that it should be from one and a half pounds to one and threequarter pounds per superficial foot. This at eight cents per pound is under thirteen cents per foot superficial. Now, sheet-lead cannot be used lighter than six pounds per foot superficial for the same purpose, which atseven cents per foot--the present price-would be forty-two cents for the foot superficial; and the leaded zinc weighing one and three-quarters pound per foot is, for roofing purposes, in every respect equal, and in many superior, to a sheet of six pound lead per foot. Leaded zinc can be used with advantage for many purposes to which lead is not applicable on account of its great weight, deficient hardness, stiffness, and strength, and to which, zinc is not applicable on account of its great susceptibility to the action of the atmosphere and other oxidizing agents. The means we use to coat the zinc with lead are as follows: A suitable quantity of lead should be placed in an iron or other suitable pan of the proper shape and size to mold a slab suitable for forming a sheet by extension between rollers, and kept at a heat little above the melting-point of zinc. A proper quantity otzincsay three times the bulk of the lead, either solid or melted-4s to be placed or poured on the lead. It placed in solid, it is to be allowed to melt, and it the two metals get mixed they must be kept in a fluid state a suflicient time for separation by the difi'erence of gravity, and also that any impurities in either metal may rise to the surface and be skimmed oft the zinc. When thus prepared the metal should be allowed to cool down to about 300 Fahrenheit, (which is the best rolling-heat of zinc,)*a-nd then extended by rolling, as required; or the metal may be allowed to become cold, and then laid by temporarily as a slab, ready to be reheated for rolling afterward.

Another process may be used for uniting the lead and zinc, viz: Make a slab of zinc by any convenient means, rectangular in form and of any suitable s-izesay eighteen by twenty-four inches, and three-eigh ths of an inch thick--with a rim all round the edges ot'one side one-eighth of an inch high, forming a kind of tray of that depth, to be filled with molten lead. Preparatory to pouring the lead into the zinc tray the latter must be heated to a few degrees above the melting-point of lead, its surface rubbed over with plumbers flux and with a stick of lead to give it a thin coating of the latter, so that when the tray is filled with melted lead the two metals, when cold, shall be united together to form a solid slab.

The proportions of lead and zinc may be varied according to the use for which the coated sheets ofzinc are intended; but we consider the best proportions to be about one-quarter lead and three-quarters zine. The thickness of the slab when made may be varied alsoybut we consider the best thickness to be from half to about three-quarters of an inch.

Then a compound slab of zinc and lead has been formed the next operation is to extend it into a sheet, so that when finished one side will be of lead and the other zinc, or ot'zinc covered on both sides with lead, with a smooth and even snrl'aoe. Thisis done by passing it be tween ordinary laminatingrollers; and to give the metal the requisite malleability we make use of an annealing-furnace to heat the slab from time to time during the process of rolling to 300 Fahrenheit.

\Ve are aware that metals have been coated one with another by washing and plating to protect them from oxidizing agents, 850; but we are not aware that zinc and lead have ever been united and rolled into united laminae of each of these metals, as above described. There fore Such a composite sheet as a new and useful manufacture or article of merchandise or trade of great value and importance, and which possesses the hardness, the stiffness, and strength of zinc with the capacity of lead to resist the action of oxidizing agents, as herein set forth.

In witness whereof we have hereunto set our signatures this Mth day of May, 1852.

' EDMUND MOREWOOD. GEORGE ROGERS. Witnesses:

JOSEPH MARQUETTE, WILLIAM EWING. 

